Manufacturing method for precise multi-pole magnetic components

ABSTRACT

A method is proposed to manufacture a precise multi-pole magnetic component for using in magnetic encoders. A special layout of the circuit pattern is designed and formed on a printed circuit board (PCB). Alternate and regular magnetic field is induced according to Ampere&#39;s law after a current flowing through the circuit on the PCB. The multi-pole magnetic component with fine magnetic pole pitch is achieved by forming the high-density circuit patterns on a substrate using the PCB technology.

This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on patent application Ser. No(s). 092124245 filed in TAIWAN on Sep.2, 2003, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a precise multi-pole magnetic component and themanufacturing method thereof. In particular, the invention pertains to aprecise multi-pole magnetic component that formed by using the printedcircuit board (PCB) technology and the corresponding manufacturingmethod.

2. Related Art

Magnetic encoders are widely used to detect the rotation speed, angleand position in many precise control systems. They are quite rigid withsimple structures, offering reliable operation in adverse environmentswhere high vibration, temperature, moisture or dust may exist. Since themotor size is getting smaller, a strict condition is required formagnetic encoders with high resolution. Therefore, conventional magneticencoders with wide magnetic pole pitch are not enough for using inprecise control systems anymore. A precise magnetic encoder consists ofa magnetic reading device and a multi-pole magnetic component with finemagnetic pole pitch. Its resolution is determined by the size of themagnetic pole pitch. The dimension of a monopole means the magnetic polepitch. A smaller of the magnetic pole pitch provides a higher resolutionin detection.

The signals in the multi-pole magnetic component can be detected using amagnetic reading device like Hall element or MR (magneto-resistance)element. The position and speed of a moving object can be obtained fromdetecting the rotation angle and direction of magnetic encoder.Generally, the multi-pole magnetic component with fine magnetic polepitch in the magnetic encoder is achieved by magnetization. Anunmagnetized magnetic component is placed onto the surface of amagnetizing head. The magnetizing coil is wound on the magnetizing headand the winding pattern is depended upon the design of the magnetizinghead. Connecting the terminals of magnetizing coil to a magnetizationmachine which can provide the magnetizing current. After releasing amagnetizing current, the strong magnetic field is induced to magnetizethe magnetic component. Therefore, a precise magnetizing head and amagnetization machine are required for narrowing the magnetic pole pitchof the multi-pole magnetic component. Traditionally, the multi-polemagnetizing head is obtained from the line-cutting process and thesmallest magnetic pole pitch can be acquired about 1 mm by magnetizationusing the magnetizing head. The magnetic pole pitch of less than 1 mm isvery difficult to achieve because it is limited by the precision of themachining tools and the bending angle of the magnetizing coils.

As described in the U.S. Pat. No. 4,920,326, the surface of themagnetizing head is divided into eight equal parts (16, 16′, 18, 18′,20, 20′. . . 30 and 30′) by line-cutting process and the magnetizingcoil (34) is wound into the groove as shown in FIG. 1. The grooves arelocated between any two parts. An alternate multi-pole magnetic fielddistribution is formed with an appropriate arrangement of themagnetizing coil. Both terminals (36 and 38) of the magnetizing coil areconnected to a magnetization machine which can provide the magnetizingcurrent. A strong magnetic field is induced instantaneously after themagnetization machine releases a magnetizing current. Then the magneticcomponent (40) is magnetized with a multi-pole structure. It is seenthat the distance between the magnetic poles is limited by the machiningtechnique and the minimum is about 1 mm. Besides, the insulating layerof the magnetizing coil can not withstand the stress and then breaks. Itis caused by the large bending angle of the magnetizing coil being usedin a magnetizing head with fine magnetic pole pitch. Therefore, a shortcircuit is happened on the bases (12 and 12′) of the magnetizing head.Since the bases are made of a ferromagnetic material with highpermeability, the magnetizing coil and head are exploded frequentlyduring the magnetization. Thus this way is very dangerous.

To overcome the limitation of 1 mm in the magnetic pole pitch, a newmagnetization method is introduced using the single-pulse magnetizingtechnique like the magnetic recording technology. The disclosed in theproceeding of Electrical Electronics Insulation Conference andElectrical Manufacturing & Coil Winding Conference (Chicago '93EEIC/ICWA Exposition, P.237–242, 1993) is shown in FIG. 2. Themagnetizing coils (200) are wound on the magnetizing head (201). Theleakage of the magnetic filed from the magnetizing head is used to writethe magnetic pole pairs (i.e. N and S pole) onto the surface of themagnetic component (202). The magnetic pole pitch of less than 1 mm isaccomplished successfully. Before magnetization, the magnetic componentis mounted on a base which is usually supported and rotated by a highprecision spindle motor. Then, the magnetic component is magnetized withmagnetic pole pairs intermittently controlling by using a magnetizationmachine. The precise position control of the spindle motor is highlyrequired; otherwise, an asymmetric magnetic file distribution willhappen in the multi-pole magnetic component after magnetization and itis not good for subsequent processing of signals. In addition, thedimension of the magnetic component must be controlled uniformly. Duringthe magnetization, the magnetic component will often collide with themagnetizing head if its radial run-out is too large and thus result indamages both of them. Moreover, the leaking gap in the magnetizing headand the air gap between the magnetizing head and the magnetic componenthave to be properly controlled. These are the key factors to affect thedimension of the magnetic pole pitch in magnetization. As the magneticpole pitch on the magnetic component gets smaller, the leaking gap inthe magnetizing head has to be narrowed as well. The air gap between themagnetizing head and the magnetic component must be appropriately tunedto obtain the desired magnetic pole pitch. Therefore, the manufacturingof a multi-pole magnetic component can be accomplished only under aprecise controlling in magnetization and it is difficulty.

Besides, the waveform of the magnetizing current from the magnetizationmachine is required to modify in order to magnetize the magneticcomponent with different magnetic properties using the single-pulsemagnetizing technique. Because the waveform of the magnetizing currenthighly depends upon the magnetic material property and this can beachieved only through a precise magnetization machine. In addition tocontrolling the tiny radial run-out and the material homogeneity on themagnetic component, it has to be mounted on a spindle motor under aprecision position control. The desired magnetic pole pitch can beaccomplished by tuning an appropriate leaking gap and the magnetizingair gap during the magnetization. Despite the fact that this techniquecan narrow the magnetic pole pitch to around 200 μm, the process is verycomplicated and difficult. The high precision machining, the techniquesfor making the precise magnetizing head and the magnetization machineare essential, and therefore the single-pulse magnetizing technique iscostly and not economical at all.

SUMMARY OF THE INVENTION

In view of the foregoing problems in the prior art, the inventionprovides a precise multi-pole magnetic component and the correspondingmanufacturing method. Using the electromagnetic principles, anappropriate circuit pattern is designed and formed on the printedcircuit board (PCB). An alternate and regular magnetic pole distributionis induced after a current is supplied to the circuit and then amulti-pole magnetic component is formed. The fine magnetic pole pitch inthe multi-pole magnetic component is obtained from making thehigh-density wire circuit on the substrate using PCB manufacturingtechnology.

According to electromagnetism, supplying a long straight wire with acurrent will induce an annular magnetic field around the wire. Themagnetic flux density is proportional to the current input, butinversely proportional to the distance. The invention designs a specialcircuit pattern and then it is formed on the PCB. After supplying acurrent to the circuit, the magnetic field is generated and itsdistribution is determined by the circuit pattern. Using this propertyand designing a special circuit pattern possessing with a meanderstructure, let the current flow in opposite directions on the circuit togenerate an alternate magnetic pole distribution. At present, theminimum wire width on the circuit can be achieved is about 75 μm usingPCB manufacturing technology. Thus the multi-pole magnetic componentwith fine magnetic pole pitch can be accomplished by forming the specialcircuit pattern on the PCB.

This disclosed precise multi-pole magnetic component can have bothsingle-layer and multi-layer structures. The single-layer structurecontains a substrate and a circuit built on the surface of thesubstrate. The multi-layer structure has more than one layer of circuitbuilt on the surface of the substrate. An insulating layer is insertedbetween any two layers of circuits. All circuits on different layers areconnected into a single circuit by drilling holes and filling them withsoldering tin. On the top circuit layer, the current input and output(I/O) terminals are reserved for connecting to a current source. Aftersupplying a current, the multi-layer structure can enhance the magneticfield and it is good for signal detection.

The above-mentioned precise multi-pole magnetic component can beaccomplished using the PCB manufacturing technology. The size of themagnetic pole pitch is closely related to the manufacturing technologyand the minimum value of 150 μm can be easily achieved at present. ThePCB manufacturing technology greatly improves the resolution of magneticencoders for high precision requirements.

We give a list of comparison among the conventional magnetizationtechnology, the single-pulse magnetization technology, and the PCBmanufacturing technology in Table 1.

TABLE 1 Basic Magneti- Mag- Minimum Requirements zation netizingPrecision Pole Technology Machine Head Machining Pitch PriceConventional Yes Yes Yes  ~1 mm High Magnetization Single-Pulse Yes YesYes ~200 μm Very High Magnetization PCB No No No ~150 μm CheapManufacturing Technology

To obtain a precise multi-pole magnetic component for being used inmagnetic encoders. The precision machining, the magnetizing head andmagnetization machine are necessary in the prior art for narrowing thepitch size to improve the resolution of magnetic encoders. Otherwise, itis impossible to do the job and the manufacturing cost is thus veryhigh. However, if one uses the disclosed PCB manufacturing technology tomake the precise multi-pole magnetic component with fine magnetic polepitch, neither the precision machining nor the uses of magnetizing headand magnetization machine are required. The invention is not only simplebut also completely feasible. PCB manufacturing technology is convenientfor mass production at a lower cost.

The multi-pole magnetic field distribution of the disclosed precisemulti-pole magnetic component is not formed by actually magnetizing amagnetic component. It is generated from supplying a current into thecircuit on the PCB. One can readily obtain a desired precise multi-polemagnetic field distribution by designing an appropriate circuit patternon a substrate using PCB manufacturing technology.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawings,which are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is the embodiment of the magnetizing head in the prior art;

FIG. 2 is the embodiment of the single-pulse magnetizing method in theprior art;

FIG. 3 is the first embodiment of the invention;

FIG. 4 is a schematic view of the magnetic field distribution in thefirst embodiment;

FIG. 5 is a schematic view of the circuit structure in the secondembodiment of the invention;

FIG. 6 is a schematic view of the magnetic field distribution in thesecond embodiment;

FIG. 7 shows the measured result of a partial magnetic fielddistribution produced by the disclosed linear 9-pole magnetic component;and

FIG. 8 shows the manufacturing procedure of the first embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The invention fabricates a special circuit pattern on the surface of asubstrate. The multi-pole magnetic field distribution is generated aftera current supplying to the circuit for producing the precise multi-polemagnetic component. Different magnetic pole pitches can be achievedeasily by modifying the circuit patterns on PCB. The multi-layerstructure of circuits is formed using PCB manufacturing processrepeatedly. It can enhance the strength of the magnetic field and thisis good for the signal detection. According to the invention, a specialcircuit pattern, which has a meander structure for providing the currentto flow in opposite directions, is designed and formed on the PCB. Thus,the magnetic field is induced in different directions among the circuitsto generate an alternate magnetic pole distribution. Then the multi-polemagnetic component is accomplished.

FIG. 3 shows the first embodiment of the invention. As shown in thephoto, on the surface of the PCB has a circuit pattern, which is alinear type extending along one-dimensional direction and has a meanderstructure for providing the current to flow in opposite directions.Therefore, magnetic fields pointing in different directions can beinduced among the circuit, thereby producing an alternate magnetic poledistribution. FIG. 4 is the schematic view of the magnetic fielddistribution in the first embodiment and the magnetic field has analternate magnetic pole distribution extending along one-dimensionaldirection. The magnetic flux density produced by the circuit pattern onthe substrate can be detected using a Hall sensor, or amagneto-resistance (MR) sensor/giant magneto-resistance (GMR) sensor.

The magnetic field distribution can be easily extended from theone-dimensional structure to a two-dimensional one. An annular meanderstructure, which provides the current to flow in opposite directions forproducing the magnetic field in different directions among the circuit,can be obtained from modifying the circuit pattern on the PCB. As shownin FIG. 5, this is the schematic view of circuit structure in the secondembodiment of the invention. An annular meander circuit pattern (110) isformed on the surface of a substrate (100). The current input terminal(111) and output terminal (112) are connected to a current source. Oncea current is supplied, an alternate magnetic field distribution isinduced among the circuit (110). The magnetic field distribution is anannular type in radial direction as shown in FIG. 6.

To prove that the magnetic field produced by the circuit with a tinywire width can be effectively detected and please refer to FIG. 7. It isthe measured results of a partial magnetic filed distribution of thedisclosed linear 9-pole magnetic component. Three consecutive magneticpoles of the magnetic flux density distributions are measured at adetection spacing of 200 μm and 300 μm above the surface by using aprecise Hall probe with a high sensitivity of 0.1 gauss. The width ofthe circuit wires on the substrate is designed and formed with 200 μmand the gap between two adjacent circuit wires is also 200 μm.Therefore, the size of the magnetic pole pitch is 400 μm. Aftersupplying 1A current, the measured magnetic field distribution is notonly uniform but also the obvious boundaries existing between themagnetic poles. The signals of the magnetic field distributions areenough to be as the signals for detection.

The precise multi-pole magnetic component made by using the PCBmanufacturing technology can also have double-layer or even multi-layerstructures to enhance the strength of the magnetic fields among thecircuits. FIG. 8 shows the manufacturing procedure of the disclosedfirst embodiment of the invention. First, a substrate is prepared (step10). The first layer of the circuit pattern is formed on the surface ofthe substrate using the PCB manufacturing technology (step 20). Aninsulating layer is then added on the circuit layer using the PCBmanufacturing technology (step 30). The second layer of the circuitpattern is formed on the insulating layer using the PCB manufacturingtechnology (step 40). Steps 30 and 40 are repeated until the desiredcircuit layers are completed. All circuits on different layers have tobe connected into a single circuit by drilling holes and filling themwith soldering tin. Only the current input and output (I/O) terminals onthe top circuit layer are reserved for connecting to a current source.Each layer of the circuit has a meander structure for providing acurrent to flow in opposite directions and then an alternate magneticpole distribution is generated. The magnetic field distribution of eachlayer of the circuit on the substrate is arranged appropriately to stackwith an enhancing configuration.

Certain variations would be apparent to those skilled in the art, whichvariations are considered within the spirit and scope of the claimedinvention.

1. A manufacturing method for precise multi-pole magnetic components,comprising the steps of: providing a substrate having at least onesurface; and forming a plurality of circuit layers having circuitsformed thereon on the surface of the substrate using the PCBmanufacturing technology, wherein a top layer of the plurality ofcircuit layers includes a current input terminal and an current outputterminal; wherein each of the circuit layers is separated from anotherby an insulating layer; the circuits on the circuit layers are connectedinto a single circuit by drilling holes filled with soldering tin; thecurrent input and output terminals on the top layer are reserved forconnecting to a current source; each of the circuit layer has a meanderstructure having a linear type extending along one-dimensional directionfor providing a current to flow in opposite directions to produce analternate magnetic pole distribution such that the magnetic fielddistribution of each of the circuit layer is arranged by way ofenhancing configuration.
 2. The manufacturing method of claim 1, whereinthe width of the circuit on each of the circuit layer is between 75 μmto 2500 μm.
 3. The manufacturing method of claim 1, wherein the gapbetween two adjacent circuits on each of the circuit layer is between 75μm to 2500 μm.
 4. A manufacturing method for precise multi-pole magneticcomponents, comprising the steps of: providing a substrate having atleast one surface; and forming a plurality of circuit layers havingcircuits formed thereon on the surface of the substrate using the PCBmanufacturing technology ,wherein a top layer of the plurality ofcircuit layers includes a current input terminal and an current outputterminal; wherein each of the circuit layers is separated from anotherby an insulating layer; the circuits on the circuit layers are connectedinto a single circuit by drilling holes filled with soldering tin; thecurrent input and output terminals on the top layer are reserved forconnecting to a current source; each of the circuit layer has a meanderstructure having an annular pattern for providing a current to flow inopposite directions to produce an alternate magnetic pole distributionsuch that the magnetic field distribution of each of the circuit layeris arranged by way of enhancing configuration.
 5. The manufacturingmethod of claim 4, wherein the width of the circuit on each of thecircuit layer is between 75 μm to 2500 μm.
 6. The manufacturing methodof claim 4, wherein the gap between two adjacent circuits on each of thecircuit layer is between 75 μm to 2500 μm.